The principal objective of this study is to investigate the possible relationship between deaths from the leukemia/lymphoma group of diseases and agricultural occupations, particularly poultry raising. Such an association, if causal, could be based on shared infection with an agent such as Marek's Disease Virus of fowl or on environmental factors peculiar to the poultry industry or agriculture more generally. The research protocol calls for the identification of all deaths from this group of diseases in the state of Illinois, Indiana and Wisconsin during the years 1972 through 1975. Death certificates of persons residing in localities of less than 50,000 population will be matched by age (5 year groups), sex, race and county of residence with those of persons dying from all other causes except trauma. Questionnaires will then be sent to the survivors of cases and controls in order to obtain details on life-time occupation and residence. Traditional methods of retrospective analysis will be applied to determine relative risk based on occupation and residence, and possible influence of age, sex and race. Deaths from pancreatic carcinoma will be identified, matched, and investigated in exactly the same manner, as a methodologic control on the investigative procedures.